Viscous clutch for engine cooling fan

Abstract

This viscous fluid fan drive clutch has a chamber divider and flow control ring at the face of the clutch plate which prevents fluid bypass of the shear zone and features flow blocker arms depending from the ring which fit within fluid fill passages in the clutch plate to tailor the response time of the clutch.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A bladed fan and hydraulic clutch assembly for inducing a flow of cooling air through a radiator in which engine coolant is circulated comprising an input shaft member adapted to be rotatably driven, clutch plate means rotatably driven by said shaft member, said clutch plate means having a plurality of axially extending and concentric lands, rotatable clutch body means axially spaced from said clutch plate means having a plurality of axially extending and concentric lands interleaved with said lands of said clutch plate means to form a fluid shear zone therebetween, a pump plate fixed to said clutch body means and encasing said clutch plate in said clutch body means, reservoir means for containing a quantity of viscous shear fluid for operating said clutch assembly, an outlet opening for said reservoir, control means for opening and closing said outlet opening, axially extending openings formed in the face of said clutch plate and extending to the concentric lands thereof, annular fluid seal ring means adjacent to said clutch plate openings and operatively interposed between said pump plate and said clutch plate to slidably contact said pump plate and block the flow of fluid outwardly therefrom and blocker arm means extending inwardly from said fluid seal ring means and directly into said axially extending openings for partially blocking a portion of said openings to restrict the flow of fluid therethrough to thereby control the engagement of said clutch, fan blade means extending from said clutch body means, said pump plate having pumping means associated therewith to pump fluid exiting from said shear zone back to said reservoir. 
     
     
       2. The assembly defined in claim 1 wherein said blocker arm means has an outer face offset from said seal ring means and spaced from said pump plate to minimize frictional drag between said ring and said pump plate. 
     
     
       3. A bladed fan and hydraulic clutch assembly for inducing a flow of cooling air through a radiator in which engine coolant is circulated comprising an input shaft member adapted to be rotatably driven, clutch plate means rotatably driven by said shaft member, said clutch plate means having a plurality of axially extending and concentric lands, axial viscous fluid flow opening means through at least a portion of said clutch plate means communicating with said lands, clutch body means axially spaced from said clutch plate means having a plurality of axially extending and concentric lands interleaved with the lands of said clutch plate means to form a fluid shear zone therebetween, a pump plate secured to said clutch body means and encapsulating said clutch plate means, a cover plate fixed to said clutch body means, a reservoir for viscous shear fluid for said clutch assembly, a fluid for said clutch assembly, a fluid supply passage in said pump plate, control means for opening and closing said supply passage, annular seal ring means interposed between said pump plate and said clutch plate and adjacent to said axial flow opening means for diverting said clutch fluid into said shear zone through said axial flow openings means so that said clutch body means can be rotatably driven by said clutch plate means through the shear of fluid therein, fan blade means extending from said clutch body means, and pumping means outboard of said seal ring means for pumping clutch fluid from the shear zone into said reservoir and blocker arm means extending radially inward from said seal ring means for filling a portion of said axial flow opening means to restrict the effective size of the opening and thereby control the rate of fluid flow to said shear zone. 
     
     
       4. The assembly of claim 3 wherein said blocker arm means is offset from the plane of said ring to fill a portion of said axial flow openings and to provide clearance from said pump plate to reduce frictional drag between said ring and said pump plate.